72 

 « 

 we will be concerned in the f ollovang predominately with 

 hypertrophies produced under the action of external factors 

 in celJLs of the permanent tissue. (Divisions 3,4, 5.) 



gc HYPBRHYPT^IC TISSUES . 



We will term hyperhydxic all those abnormal tissues 

 whose formation is to be traced back obviously to an excess 

 of water within the plant. This excess can be produced 

 on the one hand by super-abimdant absorption, on the other 

 hand by its reduced transpiration. The decrease of this 

 transpiration may be necessitated by the increasded humi- 

 dity of the surrounding atmosphere, by ?;hich the transpira- 

 tion of the plant is arrested, or by a weakening of the 

 transpiration ability of the plant, or finally may arise 

 after the destruction of the transpiratory organs. 



It v\?ill be seen that the hyperhydric tissues form 

 an homogeneous group not only from an etiological point of 

 view, but also histologically:- they all arise from abnor- 

 mal enlargement of the cells, for v;hich reason they are to 

 be included among hypertrophies. Further, among these, are 

 entirely lacking cases in which a prosoplastic fuansforma- 

 tion of the cells (characteristic formation of the membrane) 

 the c ell- contents , etc,) is associated with the abnormal 

 increase in volume. We see rather in the majority of cases 

 thatj in the production of abnormally large cells, their 

 cytoplasmic content' decreases and its elements already 

 formed, such as the chlorophyll grains, gradually degenerate, 

 Further characteristics of hyperhydric cells and tissues 

 will be reported later. 



In cases strongly affected, a division of the single 

 elements in some plants and in certain tissues at times, 

 follows the cell" enlargement. As all the groups and sub- 

 groups, which we have set up, may not be separated from 

 (75) bne another by completely .sharp boundaries, an inclination 

 towards hyperplastic tissue changes manifests itself at 

 times even in the hyperhydric tissues. Nevertheless, all 

 hyperhydric tissues may readily be united for a common dis- 

 cussion in the present chapter, 



a. Lenticels and bark excresences . 



As is well-known, if the cuttings of v/illow, poplar j 

 alder, etc. are placed in water or in moist air, more or 

 less extensive masses of white tissue, usually very porous, 

 are formed on the lenticels of the cuttings, Schenckl in- 

 vestigated nidre closely these v\rell-known outgrowths^ first 

 of all on the parts of Salix viminalis growing under water. 



1. Ueb. d. Aerenchym, ein dgm Kovk homologes Gewebe. 

 Pringsheim's Jahrb. f. v/iss. Bgt,, 1889, Bd. XX, p. 566. 



2, De Candolle Men s. 1. lenticelles des arbres et le 

 devel, d. racinOs qui en sortent. Ann. Sc. Nat. 1826, T.VII; 

 Mohl, Sind die Lenticellen als Wurzelknospen zu betrachten? 

 Flora, 1832, Bd. XT, p. 65. 



